I just completed 192 hour tests on some more white LEDs.
The beam shots (through white plexi at 0 distance) show the tested LED on the left and the control (matched and not driven during test) on the Right.
First is a white 5mm LED just purchased from "Light of Victory" and overdriven at 30ma. The camera recorded a mild color shift and very light fade. Very good performance. These cost more than the typical 10 cent ebay LEDs but they are brighter and have good lumen maintenance. They do vary from LED to LED in color, but not quite like the Luxeon lottery:laughing:. These are claimed to be 55cd and I don't have the equipment verify. They are about 20 Deg spread and are about as bright as superbright LEDs expensive 15 Deg 18cd. These are good LEDs. Highly recommended.
Next I look at medium power LEDs. In the second picture, left side shows the .5 watt 8mm 140 Deg "straw hat" LED from ebayer cece718. The 3rd picture shows the severe fade and purple shift. .5 watt my a..:devil:! This three die LED was driven at only 100ma (140ma would have been .5w) and shows darkening above the dies. Perhaps heatsinking would have helped, but I doubt it would have made much difference. I estimate that these LEDs should not be used over 50-60ma. They are consistent from sample to sample with a violet tinged white. I can't recommend these given the severe fading at underdrive.
The LED on the right in the 2nd picture is the "Light of Victory" 10mm .5w 280cd 4 die LED. Driven at 100ma for 8 days show some fading. Like the other high power LED, I did not heatsink well, but it faded much less (last pix). These have much heavier leads than a 5mm and the cathode (die cup side) should be soldered to a board with adequate copper area to help dissipate heat. In that case, this LED would likey perform fine. At around 60 cents each I recommend these LEDs. If your not going to heatsink them, run them at 80ma.
Thanks for looking, John
The beam shots (through white plexi at 0 distance) show the tested LED on the left and the control (matched and not driven during test) on the Right.
First is a white 5mm LED just purchased from "Light of Victory" and overdriven at 30ma. The camera recorded a mild color shift and very light fade. Very good performance. These cost more than the typical 10 cent ebay LEDs but they are brighter and have good lumen maintenance. They do vary from LED to LED in color, but not quite like the Luxeon lottery:laughing:. These are claimed to be 55cd and I don't have the equipment verify. They are about 20 Deg spread and are about as bright as superbright LEDs expensive 15 Deg 18cd. These are good LEDs. Highly recommended.
Next I look at medium power LEDs. In the second picture, left side shows the .5 watt 8mm 140 Deg "straw hat" LED from ebayer cece718. The 3rd picture shows the severe fade and purple shift. .5 watt my a..:devil:! This three die LED was driven at only 100ma (140ma would have been .5w) and shows darkening above the dies. Perhaps heatsinking would have helped, but I doubt it would have made much difference. I estimate that these LEDs should not be used over 50-60ma. They are consistent from sample to sample with a violet tinged white. I can't recommend these given the severe fading at underdrive.
The LED on the right in the 2nd picture is the "Light of Victory" 10mm .5w 280cd 4 die LED. Driven at 100ma for 8 days show some fading. Like the other high power LED, I did not heatsink well, but it faded much less (last pix). These have much heavier leads than a 5mm and the cathode (die cup side) should be soldered to a board with adequate copper area to help dissipate heat. In that case, this LED would likey perform fine. At around 60 cents each I recommend these LEDs. If your not going to heatsink them, run them at 80ma.
Thanks for looking, John
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